Influence of fault slip rate on shear‐induced permeability

Abstract

[1] We measured permeability in sandstone and granite sheared at slip rates from 10 −4 to 1.3 m/s under low-normal stress at confining pressures up to 120 MPa. As the slip rate increased, the permeability of Berea sandstone decreased by an order of magnitude, whereas that of Indian sandstone and Aji granite increased by 3 orders of magnitude at high slip rates. A fine-grained gouge layer of thickness developed during slip, and the wear rate was increased abruptly at high slip rates. Microcracks and mesoscale fractures formed at slip rates above 0.13 m/s. Numerical modeling showed that the slip surface temperature increased by several hundred degrees for slip velocities above 0.13 m/s and exceeded the a-b phase transition temperature of quartz at 1.3 m/s. Both the temperature rise and the temperature gradient at the slip surface were high at fast slip rates. We attributed reduced permeability after slip in porous sandstone to the low-permeability gouge layer. An abrupt permeability increase in low-permeability rocks at high slip rates was caused by heat-induced cracks. An increase in the rate of wear of gouge with increasing slip velocity was caused by frictional heating that reduced the rock strength. The host-rock permeability that separated reductions and increases in permeability was about 10 −16 m 2 at 10 MPa effective pressure. Our results suggest that abrupt increases in shear stress during slip in a low-permeability fault zone caused by thermal cracking, which may decrease the total slip displacement. The abrupt permeability increase at high slip rates in low-permeability rocks agrees with hydrogeochemical phenomena observed after earthquakes.

Influence of Normal and Shear Stress on the Hydraulic Transmissivity of Thin Cracks in a Tight Quartz Sandstone, a Granite, and a Shale

“…These effects are well known from previous experimental studies (e.g., Chen et al, 2015;Cuss et al, 2011;Engelder & Scholz, 1981;Guo et al, 2013;Kranz et al, 1990;McKernan et al, 2017;Tanikawa et al, 2010;Zhang et al, 2013Zhang et al, , 2015Zimmerman & Bodvarsson, 1996). In experiments designed to investigate the effect of low amplitude fluid pressure oscillations of seismogenic origin on permeability of Berea sandstone, Elkhoury et al (2011) andCandela et al (2015) reported permeability enhancements by up to 50% following fluid pressure oscillations of 20 s period for 3 min.…”

Pressure dependence of fluid transport properties of shallow fault systems in the Nankai subduction zone

“…However, transport properties will evolve by rapid shear deformation, which can drastically change the permeability of fault rocks (Tanikawa et al 2010). Tanikawa et al (2012) performed shear-induced permeability tests at a high-velocity condition on simulated fault gouge samples from core materials taken from the megathrust fault and the frontal thrust.…”

A scenario for the generation process of the 2011 Tohoku earthquake based on dynamic rupture simulation: Role of stress concentration and thermal fluid pressurization

“…However, since the restraining effect strongly depends on the constitutive law of porosity evolution, this issue is still under debate. More experimental support, such as that provided by Tanikawa et al (2010), is necessary to clarify this problem. Lastly, the effect of offfault plastic yielding can restrain the dynamic-weakening effect (e.g., Andrews, 2005;Dunham et al, 2011).…”